# CVE-2026-21871: PYSEC-2026-1698 - NiceGUI is vulnerable to XSS via Unescaped URL in ui.navigate.history.push() / replace()

Source: https://junglewise.ai/threats/cve-2026-21871-nicegui-is-vulnerable-to-xss-via-unescaped-url-in-ui-navigate  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-07  
License: CC BY 4.0 with a link back

CVE-2026-21871 · Severity: low · CVSS 3.1 · Published 2026-07-07

NiceGUI is vulnerable to XSS via Unescaped URL in ui.navigate.history.push() / replace()

Technologies: [nicegui (PyPI)](https://junglewise.ai/threats/technologies/nicegui). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-21871 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-21871 being exploited in the wild.

**How severe is CVE-2026-21871?** Low severity, with a CVSS score of 3.1, published 7 July 2026.

**Which products and versions are affected?** nicegui (PyPI) ECOSYSTEM:introduced=2.13.0,fixed=3.5.0.

**Is there a fix for CVE-2026-21871?** Yes. nicegui (PyPI): upgrade to 3.5.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2026-21871?** Check whether you run nicegui (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- nicegui (PyPI): upgrade to 3.5.0 or later

  ```sh
  pip install "nicegui>=3.5.0"
  ```


## Affected products

- nicegui (PyPI) ECOSYSTEM:introduced=2.13.0,fixed=3.5.0

## Identifiers

- CVE-2026-21871
- GHSA-7grm-h62g-5m97
- PYSEC-2026-1698

## Related threats

- [PYSEC-2026-1703 - NiceGUI has Redis connection leak via tab storage causes service degradation](https://junglewise.ai/threats/cve-2026-21874-nicegui-has-redis-connection-leak-via-tab-storage-causes-service)
- [PYSEC-2026-1702 - NiceGUI apps which use `ui.sub_pages` vulnerable to zero-click XSS](https://junglewise.ai/threats/cve-2026-21873-nicegui-apps-which-use-ui-sub-pages-vulnerable-to-zero-click-xss)
- [PYSEC-2026-1701 - NiceGUI apps are vulnerable to XSS which uses `ui.sub_pages` and render arbitrary user-provided links](https://junglewise.ai/threats/cve-2026-21872-nicegui-apps-are-vulnerable-to-xss-which-uses-ui-sub-pages-and)
- [PYSEC-2026-1697 - NiceGUI Reflected XSS in ui.add_css, ui.add_scss, and ui.add_sass via Style Injection](https://junglewise.ai/threats/cve-2025-66469-nicegui-reflected-xss-in-ui-add-css-ui-add-scss-and-ui-add-sass)
- [PYSEC-2026-1699 - NiceGUI has a Reflected XSS](https://junglewise.ai/threats/cve-2025-53354-nicegui-has-a-reflected-xss)